|  | 1.1 | The OSI Reference Model and the Problems it Solves
| 1.1.2 | The OSI model layers
Each layer of the OSI reference model serves a specific function: Application layer (Layer 7) -This layer provides network services to user applications. For example, a word processing application is serviced by file transfer services at this layer. Presentation layer (Layer 6) -This layer provides data representation and code formatting, along with the negotiation of data transfer syntax. It ensures that the data that arrives from the network can be used by the application, and it ensures that information sent by the application can be transmitted on the network. Session layer (Layer 5) -This layer establishes, maintains, and manages sessions between applications. Transport layer (Layer 4) -This layer segments and reassembles data into a data stream. The transport layer has the potential to guarantee a connection and offer reliable transport. Network layer (Layer 3) -This layer determines the best way to move data from one place to another. The router operates at this layer. This layer uses logical addressing schemes that can be managed by an administrator. This layer uses the Internet Protocol (IP) addressing scheme, along with Apple-Talk, DECnet, VINES, and IPX addressing schemes. Data link layer (Layer 2) -This layer provides physical transmission across the medium. It handles error notification, network topology, and flow control. This layer uses Media Access Control (MAC) addresses, which also are referred to as physical or hardware addresses. Physical layer (Layer 1) -This layer provides the electrical, mechanical, procedural, and functional means for activating and maintaining the physical link between systems. This layer uses such physical media as twisted-pair, coaxial, and fiber-optic cable.
| Lab Activity
This lab will serve as a refresher to reinforce understanding of the seven layers of the OSI model as they relate to the TCP/IP model. Focus is on where terms and devices fit in the OSI model. This lab can be a fun collaborative knowledge competition activity.

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